The present invention relates to a process for the production of hydrogen by catalytic reforming of methanol with water vapor.
The process produces hydrogen with carbon dioxide as the principal impurity.
At the present time it is known that the major part of the hydrogen used in the world comes from the catalytic reforming of natural gas.
The latter is not always available at the desired location. Also, for the limited needs of some places, it is preferred to start from liquid charges more easily storable than methanol.
The production of hydrogen from methanol is based on the well-known reaction (FR-1549 206 and 1599 852) of reforming methanol with steam: EQU CH.sub.3 OH+H.sub.2 O.revreaction.CO.sub.2 +3H.sub.2 (1)
which can theoretically be employed in the presence of any one of the catalysts already proposed for the reverse reactions of methanol synthesis: EQU CO+2H.sub.2 .revreaction.CH.sub.3 OH (2) EQU CO.sub.2 +3H.sub.2 .revreaction.CH.sub.3 OH+H.sub.2 O (3)
In practice however when it is sought to reform methanol, an accelerated deactivation of the catalytic system is experienced. The same observation has been made by the applicants of Belgian Pat. No. 884720 who propose to remedy this either by the use of modified catalysts, less active at low temperature, or by the use of a particular starting method, or lastly by the use of two successive catalyst beds, one for performing the cracking of the methanol according to the reverse reaction (4) from reaction (2): EQU CH.sub.3 OH.revreaction.CO+2H.sub.2 ( 4)
the other for converting the carbon monoxide obtained: EQU CO+H.sub.2 O.revreaction.CO.sub.2 +H.sub.2 ( 5)
It has now been found that the employment of these measures is not necessary and that it suffices to avoid the deactivation of a catalyst containing copper, to add a critical proportion of carbon dioxide to the reagents, water and methanol, before putting them into contact witht he catalyst.
It is known that the massive injection of CO.sub.2 into the reforming system of methanol with steam is an effective though expensive means for increasing the ratio CO/H.sub.2 of the synthesis gas manufactured.
Thus, the Belgian patent alreay cited teaches that, by varying the molar ratio CO.sub.2 to methanol between 0.8 and 2.4, it is possible to change the content of CO of the manufactured gas from 31 to 41% by volume approximately, with a simultaneous lowering of the yield of hydrogen.